Petr Raušer

Novel biodegradable polydioxanone stents in a rabbit airway model

OBJECTIVE This study was undertaken to evaluate safety and biocompatibility of a novel biodegradable polydioxanone stent in a rabbit tracheal model. Metallic and silicone stents represent standard therapeutic approaches for hollow organ stenosis, although complications have been reported repeatedly. Biodegradable stents could reduce the risks associated with this procedure while still achieving the purpose of maintaining lumen patency. METHODS A commercially available polydioxanone suture strand with a long safety record was used to manufacture the self-expanding stents. The polydioxanone stents were then implanted bronchoscopically and under fluoroscopic guidance into the tracheas of white rabbits (N = 25). Periodic clinical examination was performed. Histopathologic examination concluded the study for the 5 experimental groups at 3, 4, 5, 10, and 15 weeks after implantation. RESULTS There were no unexpected deaths and no stent displacements during the study. The animals remained in good condition, without stent debris expectoration. Macroscopic examination revealed that the tracheal lumen stayed open. Histologic examination showed that tracheal damage score was highest 5 weeks after stenting, including in-stent necrosis of the epithelium. Stent degradation was complete with no remnants after 10 weeks, leaving the trachea completely healed at 15 weeks after implantation. CONCLUSIONS This animal airway model has demonstrated acceptable safety and biocompatibility of this novel biodegradable polydioxanone stent. We suggest that polydioxanone stenting be used for further clinical studies for cases in which complete stent degradation after temporary airway treatment is desirable.

Effect of medetomidine-butorphanol and dexmedetomidine-butorphanol combinations on intraocular pressure in healthy dogs.

OBJECTIVE To assess the effects of intravenous (IV) medetomidine-butorphanol and IV dexmedetomidine-butorphanol on intraocular pressure (IOP). STUDY DESIGN Prospective, randomized, blinded clinical study. ANIMALS Forty healthy dogs. Mean ± SD body mass 37.6 ± 6.6 kg and age 1.9 ± 1.3 years. METHODS Dogs were allocated randomly to receive an IV combination of dexmedetomidine, 0.3 mg m(-2), combined with butorphanol, 6 mg m(-2), (group DEX) or medetomidine 0.3 mg m(-2), combined with butorphanol 6 mg m(-2), (group MED). IOP and pulse (PR) and respiratory (f(R) ) rates were measured prior to (baseline) and at 10 (T10), 20 (T20), 30 (T30) and 40 (T40) minutes after drug administration. Oxygen saturation of hemoglobin (SpO(2)) was monitored following sedation. Data were analyzed by anova followed by Dunnetts tests for multiple comparisons. Changes were considered significant when p < 0.05. RESULTS Following drug administration, PR and f(R) were decreased significantly at all time points but did not differ significantly between groups. Baseline IOP in mmHg was 14 ± 2 for DEX and 13 ± 2 for MED. With both treatments, at T10, IOP increased significantly (p < 0.001), reaching 20 ± 3 and 17 ± 2 for DEX and MED respectively. This value for DEX was significantly higher than for MED. There were no significant differences in IOP values between groups at any other time points. At T30 and T40, IOP in both groups was below baseline (DEX, 12 ± 2 and 11 ± 2: MED 12 ± 2 and 11 ± 2) and this was statistically significant, for DEX. CONCLUSIONS AND CLINICAL RELEVANCE At the documented doses, both sedative combinations induced a transient increase and subsequent decrease of IOP relative to baseline, which must be taken into consideration when planning sedation of animals in which marked changes in IOP would be undesirable.

Incidence of seizures associated with iopamidol or iomeprol myelography in dogs with intervertebral disk disease: 161 cases (2000-2002).

OBJECTIVE To compare the incidence of seizures in dogs with intervertebral disk disease after iopamidol or iomeprol myelography, and to assess whether the incidence of seizures differed between the 2 agents when severity of neurological deficits, location of cord compression, duration of anesthesia, site of myelogram, volume of contrast, and concentration of contrast were evaluated. DESIGN Retrospective study. SETTING Veterinary teaching hospital. ANIMALS One hundred and sixty-one client-owned dogs with intervertebral disk disease. INTERVENTIONS Subarachnoid injection of contrast medium. MEASUREMENTS AND MAIN RESULTS One hundred and sixty-one dogs with intervertebral disk disease were subjected to myelography using iopamidol (n=74) or iomeprol (n=87). Cranial myelography was performed in 31 dogs, caudal myelography in 125 and both cranial and caudal myelography in 5. Seizures occurred in 23 of 161 (14%) dogs. There was no significant difference overall between iopamidol and iomeprol myelography. However, in dogs with thoracolumbar disk extrusion and paraplegia, seizures occurred more frequently after caudal myelography using iopamidol compared with iomeprol. CONCLUSIONS Both iomeprol and iopamidol are suitable for myelography in dogs. Iomeprol is recommended for caudal myelography in paraplegic dogs with thoracolumbar disk extrusion due to the higher incidence of seizures in this group when iopamidol was used.

Intracoronary Delivery of Bone Marrow Cells to the Acutely Infarcted Myocardium

Objectives: Intracoronary cell transplantation during catheter balloon inflations may be associated with adverse events. We studied the effectiveness of an alternative transplantation technique – intracoronary cell infusion. Methods: Fourteen pigs, which had survived acute myocardial infarction, were randomized into 2 treatment groups and 2 controls. Three days after infarction, 12 pigs underwent allogeneic intracoronary mononuclear bone marrow cell transplantation using either the standard technique (short-term cell injections during repeat balloon inflations, technique A, n = 6) or continuous intracoronary cell infusion without balloon inflations (technique B, n = 6). Implanted cells were stained with fluorescent dye. After transplantation, the pigs were euthanized and myocardial samples were analyzed by fluorescent microscopy. Results: The mean numbers of fluorescently labeled bone marrow cells in the infarction border zone, in the infarction mid-area and in the center of myocardial infarction were 84, 72 and 55 using technique A, and 29, 57 and 46 using technique B, respectively. The mean cell retention in the infarction border zone of 84 cells for technique A and 29 cells for technique B differed significantly (p = 0.034, two-tailed t test). Conclusion: The continuous intracoronary cell infusion technique is a less efficient cell delivery technique as compared with the standard technique using repeat intracoronary balloon inflations.

Experimental model of myocardial infarction: Histopathology and reperfusion damage revisited

The goal of this pilot study was to create an experimental model of myocardial infarction (for subsequent evaluation of the effectiveness of an alternative way of stem cell application - intracoronary cell infusion in the management of acute myocardial infarction). Four experimental animals, female pigs weighing between 30 and 40 kg, were used in the initial phase of this study to create an experimental model of acute myocardial infarction. An experimental myocardial infarction was performed via occlusion of the interventricular arm of the left coronary artery for 90 min. The hearts were examined 1 h, 3 days, 5 days, and 7 days after the procedure. Macroscopically, red infarction characteristic of reperfusion was found. Microscopically, the healing process with granulation tissue production/collagen deposition was remarkably accelerated compared to literature data. Repair processes in reperfused experimental myocardial infarction and/or reperfused autopsy specimens should not be evaluated on the basis of literature data only. Large collections of extracellular calcium were present. This phenomenon is not well described in the literature and probably has the potential for significantly interfering with the repair process. The histopathology of reperfused acute myoardial infarction deserves to be studied in further investigations.

Nanotechnology and mesenchymal stem cells with chondrocytes in prevention of partial growth plate arrest in pigs

INTRODUCTION This study describes the results achieved using a combination of allogeneic mesenchymal stem cells (MSCs) with chondrocytes (CHC) and a new scaffold consisting of type-I collagen and chitosan nanofibers in the prevention of partial growth plate arrest after iatrogenic injury in pigs. MATERIAL AND METHODS The miniature pig was selected as an experimental model to compare the results in the left femoral bones (MSCs and CHC in scaffold transplantation into the iatrogenic partial distal growth plate defect) and right femoral bones (scaffold alone transplantation). The experimental group consisted of 10 animals. Bone marrow from os ilium as the source of MSCs was used. A porous cylinder consisting of 0.5% by weight type-I collagen and 30% by weight chitosan, was the optimal choice. The length of the bone and angular deformity of distal femur after the healing period was measured and the quality and structure of the newly formed cartilage was histologically examined. RESULTS Transplantation of the composite scaffold in combination with MSCs and chondrocytes led to the prevention of growth disorder and angular deformity in the distal epiphysis of the left femur. Compared to the right (control) femur, tissue similar to hyaline cartilage with signs of columnar organization typical of the growth plate occurred in most cases. CONCLUSIONS The promising results of this study reveal the new and effective means for the prevention of bone bridge formation after growth plate injury.

Semi-spherical Radiofrequency Bipolar Device - A New Technique for Liver Resection: Experimental In Vivo Study on the Porcine Model.

The incidence of colorectal carcinoma is still growing in the Czech Republic and also all around the world. With success of oncological treatment is also growing a number of potential patients with liver metastases, who can profit from surgical therapy. The aim of this study was to confirm on porcine models that this method by using new surgical device is effective and safe for patients who have to undergo liver resection. The primary hypothesis of the study was to evaluate whether this new device is able to consistently produce homogeneous and predictable areas of coagulation necrosis without the Pringle maneuver of vascular inflow occlusion. The secondary hypothesis of the study was to compare the standard linear radiofrequency device and a new semi-spherical bipolar device for liver ablation and resection in a hepatic porcine model. Twelve pigs were randomly divided into two groups. Each pig underwent liver resection from both liver lobes in the marginal, thinner part of liver parenchyma. The pigs in first group were operated with standard using device and in the second group we used new developed semi-spherical device. We followed blood count in 0th, 14th and 30th day from operation. 14th day from resection pigs underwent diagnostic laparoscopy to evaluate of their state, and 30th day after operation were all pigs euthanized and subjected to histopathological examination. Histopathological evaluation of thermal changes at the resection margin showed strong thermal alteration in both groups. Statistical analysis of collected dates did not prove any significant (p < 0.05) differences between standard using device and our new surgical tool. We proved safety of new designed semi-spherical surgical. This device can offer the possibility of shortening the ablation time and operating time, which is benefit for patients undergoing the liver resection.

Direct comparison of enoxaparin and nadroparin in a rabbit model of arterial thrombosis prevention

INTRODUCTION The aim of the study was to evaluate and compare the efficacy of standard unfractionated heparin (UFH) and low-molecular weight heparins (LMWHs). MATERIALS AND METHODS We modified a previously published rabbit model of arterial thrombosis prevention [1,2] to compare unfractionated heparin and two different doses of two low-molecular weight heparin fragments--nadroparin and enoxaparin. Thrombosis in the distal aorta was triggered by vessel wall injury and critical stenosis. Blood flow in the damaged arterial segment was monitored by a flow probe placed distal to the constrictor. The primary endpoints of the study were: (1) cumulative flow, (2) time to occlusion and (3) residual clot weight. Thirty six animals were split into 6 groups with six animals in each group. Control groups were given saline or heparin and four more groups were used to compare LMWHs at 2 different doses. RESULTS In our study, all treatments were superior to the saline control group (alpha<or=0,01). Standard heparin was inferior (alpha<or=0,05) to both low molecular weight heparins for all primary endpoints (cumulative flow, time to occlusion and residual clot weight). There were no differences between the LMWHs except for cumulative flow at high doses. CONCLUSIONS This study revealed no relevant differences between nadroparin and enoxaparin for the primary endpoints of our model. Clinical use of each drug remains a personal preference.

Influence of capnoperitoneum on intraocular pressure in spontaneously breathing dogs undergoing ovariectomy

The objective of this study was to evaluate potential changes in intraocular pressure in spontaneously breathing dogs undergoing laparoscopic ovariectomy with capnoperitoneum. Twenty bitches undergoing laparoscopic ovariectomy were enrolled in a prospective clinical trial. The dogs were under general anaesthesia and were breathing spontaneously throughout the entire period of the procedure. Capnoperitoneum was then established with an intra-abdominal pressure setting of 10 mmHg. Collected data included intraocular pressure, pupil size, heart rate, respiratory frequency, systolic and diastolic arterial pressure, end-tidal CO2, oxygen saturation of haemoglobin and tidal volume. Data were recorded 5 min before starting CO2-insufflation (baseline), after capnoperitoneum establishment (T0), and at further 5-min intervals (T5, T10, T15, T20, T25, T30). Compared to baseline, pupil size was increased at T30 (P = 0.03) and respiratory frequency at T25 (P < 0.01) and T30 (P = 0.02). No other significant changes were found regarding intraocular pressure. Our data show that the induction of an intra-abdominal pressure of 10 mmHg for a 30-min laparoscopy with the use of medetomidine-butorfanolpropofol-isoflurane in spontaneously breathing dogs in the horizontal position does not result in any important changes in intraocular pressure or end-tidal CO2.